KingofSling wrote on Jun 22^nd, 2009 at 12:18pm:


I started this thread to give people a better idea idea about the kinetic energy that is potentially generated with the advantage of a sling (or similar device). I am not trying to determine maximum velocity.



I am not saying you are (I never mention maximum velocity), I´m just saying the only thing you need to know is the speed of your projectile at the moment you want to know its kinetic energy (off course you allready measured its mass).
So you can get all mystical or complicated about it but it is just that simple.

A slung baseball (148 gr.) at 57m/s, RADAR.

Wanderer. Accurate means accurate, as close as possible to reality. Of course it depends on what level of "accurate" one is willing to accept. Personally I'm pleased when a shot goes where I want it to (Forwards as opposed to straight up and then down on my silly head or sideways to the consternation of onlookers ) and don't worry too much about delivered force. A martial arts mate tells me, with ghoulish relish, I think, that the human skull can be cracked with no more than 7 pounds of impact force, it still seems too little, but it makes me careful.
I think the interest in kinetic enegy comes from the use of the sling in hunting, people want to know how much is enough for various prey, it is of course the transfer of kinetic energy that causes death through shock and mechanical disruption of internal structures, organs and bones etc. Of course it may be no more than wanting to know what one is capable of in a demonstable and comparable format.
A pefectly reasonable desire given we all want to know what we can do and compare that result with others with similar interests.
I'll happily grant a time over distance calulation will give a reasonable guesstimate of velocity and therefore kinetic energy. I'd understood from the other posts that what was desired was a correct-as-possible result. To me that means a Chronograph. Despite the many difficulties in employing one.
I was trying to point out the many problems with getting such data with a sling, not trying to put any one down or upset any one.
I too, see little correlation between a sling projectile of a few ounces (or even half a brick which I tried once and it damned near too my finger off when it caught in the primitive sling I'd knocked together one boring nightshift ) and a hammer throw hammer, apart of course from the acquisition of momentum from a rotating mass.

BTW. What is a "Sound card"? Some sort of target that makes a noise when hit.
Sorry if that is a simplistic question but I've never had the opportunity to discuss this subject with others, let alone others with more experience and practice than I have. Typhon

Wanderer. You can use the sound cards on a comp to track and analyse a shot? Cool!
I'll check out the link shortly. Ta for that mate.
It certainly beats a chronograph for accuracy, I'm a little dubious about your radar analogy, but that's a side effect of my pedantic streak, I understand your meaning. That this technique is acceptably accurate, inexpensive and relies on transmission from the projectile, as opposed to bouncing a radio wave off the projectile and analysing the reflected energy.
Agreed. There is no comparison between firearm projectiles and sling projectiles. A bullet penetrates and, except in some hypothetically possible situation or those broad head tipped projectiles, a sling shot won't. It's an impact weapon only. It will break bones. bruise and shock but not penetrate.
You may be right in thinking that kinetic energy is being used to replace killing/stopping power however the mechanisms are so different between the two projectiles that no meaningful comparison can be made.  Comparing the delivered energy between a bullet and a sling shot is irrelevant as the velocity is much lower, and perhaps more importantly the bullet is much smaller, giving better penetration to the firearm for a given velocity. It's that old high school science book trick again. There's a picture of a slightly built female human in high heels and an elephant and the question is which one has the higher groung pressure. the aswer is the female human as the lighter weight is concentrates by the narrow foot print. There is no such thing as an unarmed woman in high heels, those 1/4 inch tips will go straight through a human foot or abdominal wall with a solid kick.
I suppose that there may be some overlap between very low power ammunition and large heavy sling projectiles slung fast, but I see no point in such comparison.
It is enough to know that a solid hit with a solid sling projectile can kill a rabbit , for instance. It'll do the job asked of it in a hunting or military (maybe not todays military though) setting.
Gawd I'm tired, I hope the above makes sense.  typhon

Guess what, I tried to measure the lead glandes and i couldn't. Usually what I do is use the projectile itself for the measurment , not the sounds. So I tried really hard to watch the glandes in flight and they are almost impossible to follow their paths, unlike rocks which I'm used to.

The only one I could see for sure took 15 frames to reach 20 meters and my camera tapes at 30 frames per seccond.

This comes at 40 meters per second, and with a 100 gram projectile it comes at 80 joules. I wish I had more shots available to average, but like I said, it's impossible to see them.      

Typhon wrote on Jun 26^th, 2009 at 3:03am:

I'd certainly agree with C_A here. Lead sling bullets must have penetrated flesh fairly frequently. It would be interesting to know the distribution of different kinds of sling bullet wounds during battles, but I don't think anyone was keeping the statistics back then.

Typhon, I agree with you about my hasty analogy to radar. Perhaps acoustic interferometry would be a better description.

Rockman, have you ever tried using the sound track to get your timings? Maybe it would  help in cross checking your video results.